1. Field of the Invention. This invention relates to disc brakes and more particularly disc brakes for motor vehicle wheels and the like.
2. Description of the Prior Art. Disc brakes generally comprise a rotor mounted on a wheel rotatable about an axle. An anchor member rigidly mounted to the axle, has a caliper mounted thereon which has a piston and reaction portion, each of which engages a brake shoe. The brake shoes are movable to an abutting position against two sides of the rotor. The great torque involved in slowing down a rapidly spinning wheel must be transferred from the spinning wheel and rotor to the non-rotating anchor member.
Many disc brake assemblies have the brake shoes abut the caliper to transfer the torque through the caliper and to the anchor member. Such constructions have been disclosed in U.S. Pat. Nos. 2,756,844 issued to Chamberlain et al on July 31, 1956; 3,346,075 issued to Swift on Oct. 10, 1967; U.S. Pat. No. 3,388,774 issued to Burnett on June 18, 1968; U.S. Pat. No. 3,580,362 issued to Falk on May 25, 1971; U.S. Pat. No. 3,616,877 issued to Collins on Nov. 2, 1971 and U.S. Pat. No. 3,800,923 issued to Rike on Apr. 2, 1974. The Chamberlain et al, Swift and Burnett references all disclose calipers which are mounted to the anchor member by pins or bolts. The Falk reference disclose bolts which extend through slots in the shoes. However this design, even though it balances the forces exerted on the caliper, forces the caliper to be secured in an extremely rigid fashion to the anchor plate to be able to withstand the torque loads. The extremely rigid mounting of the caliper tends to make the brake assembly prone to shudder and rough braking which is transmitted to the vehicle body and felt by the passengers.
U.S. Pat. No. 3,500,969 issued to Asher discloses brake shoes and a two-piece caliper mounted on bolts with special U-shaped arms secured to the caliper and functioning as the reaction portion of the caliper which receives torque from the braking forces exerted on the brake shoes.
U.S. Pat. No. 3,781,068 issued to Brooks discloses another brake which transmits torque through the caliper by flanges of the brake shoe abutting walls of the caliper. Pins passing through the anchor plate are used as guides for the brake pads.
Other caliper disc brake assemblies have been disclosed which eliminate the caliper undergoing the stress of the torque transfer by having the transfer of the torque pass directly from the brake shoes to the anchor member. Such direct transfers are disclosed in U.S. Pat. No. 2,781,106 issued to Lucien on Feb. 12, 1957; U.S. Pat. No. 3,081,843 issued to Dotto et al on Mar. 19, 1963; and U.S. Pat. No. 3,773,149 issued to Toshida et al on Nov. 20, 1973.
The Dotto et al patent discloses a removable pin mounting the caliper to the anchor. The Lucien patent discloses brake shoes mounted on pins for slideable movement therealong.
The advantage of the caliper not receiving torque is that smoother brake operation is possible. In addition, the caliper can be made from weight saving materials. The disadvantage with the above design is that service of the wheel bearings is more difficult due to the anchor plate hanging down on both sides of the rotor necessitating removal of the anchor plate when servicing the bearings.
U.S. Pat. No. 4,034,857 issued to Kondo et al discloses pins threaded into a lug which is welded onto the anchor plate. The pins are used for guiding the caliper. The caliper brake shoe directs torque directly to the anchor plate. The lugs slideably mount an opposing brake shoe which has apertures receiving the lugs. The problem with the Kondo disclosure is that the lugs are a permanent part of the anchor plate and cannot be easily replaced if its sliding surface which the brake shoe slides upon is damaged.
What is desired is a replaceable one-piece pin secured to the anchor plate and constructed to have sufficient strength to be used as a torque transmitting member for one brake shoe as well as a guide member for the brake shoe and simultaneously mount the caliper free from any torque transmission therethrough. The known prior art does not disclose or suggest a way to construct this desirable caliper disc brake construction.